1. Field of the Invention
The present invention is directed generally to nanofilter systems and, more particularly, to nanofilter systems in biomass conversion and recycling processes.
2. Description of the Related Art
Biomass processing involves the conversion of products, such as paper, tree pulp, and the like from cellulose to its constituent sugar molecules (i.e. glucose cellulose and mixed sugars from hemicellulose). A conventional technique for biomass processing is the treatment of the biomass with a powerful acid in a hydrolysis process. In the acid hydrolysis conversion of the lingo-cellulosic portion of the biomass into sugars, a critical step is the recovery and recycle of the acid catalyst.
The hydrolysis process results in a combination of sugars and acid. The sugar is separated from the acid and utilized in the production of fuels (e.g., ethanol, sweeteners, and/or other chemicals by a number of known techniques). The typical acid-sugar separation process uses a chromatographic separation technique to recover the sugar and to separate the sugar in the acid. Furthermore, the recovered acid may be reprocessed.
Ideally, the acid catalyst is recovered and reconcentrated for reuse in the hydrolysis reaction. The reconcentration is typically performed by thermal evaporative concentration. This process requires the removal of residual sugar.
The chromatographic separation process is imperfect and results in an acid that is contaminated with sugars. The sugar contamination poses a significant problem in the evaporation process as it leads to fouling of heat exchanger surfaces and foaming in the process equipment. Currently, the only solution to this problem is frequent mechanical and/or chemical cleaning of the process equipment and/or the chemical destruction of contaminant sugars by oxidation. Typical oxidation pathways include the use of hydrogen peroxide and/or nitric acid as a chemical oxidant. These techniques are very costly in terms of operations since they reduce the productivity of the biomass processing system. In addition, the chemical oxidants are costly. The chemical oxidation pathways also pose potential environmental emissions issues as well as safety concerns. Therefore, it can be appreciated that there is a significant need for a system and method to adequately separate sugars and acid to allow acid evaporation reconcentration processes to be used in recycling the acid. The present invention provides this, and other advantages as will be apparent from the following detailed description and accompanying figures.